In a sea water desalination facility, a membrane filtration process using a reverse osmosis membrane is broadly being applied to many industries or water treatment area as well as desalination of sea water, and its predominance has been proved in many ways such as performance or energy efficiency. On the other hand, in operating a reverse osmosis membrane filtration process, proliferation of microorganisms to the form of biofilm on the membrane surface of the treated water side (non-treated water side of the reverse osmosis membrane) causing increase of operating pressure of the reverse osmosis membrane, or biofouling (contamination caused by organism attachment) causing decrease of water permeability or separation performance of the reverse osmosis membrane become problems. The biofouling is a membrane surface fouling caused by various contaminants such as organic or inorganic floating particles, dissolved organic matters (DOM), dissolved solids and biogenic materials, and major contamination source is organic contamination related to large amount of organic matters.
“Biofilm” is a structure formed by microorganism on the pipe wall or the reverse osmosis membrane face when water flows therein, and mainly contains extra cellular polymeric substances consisting of polysaccharides, proteins and the like, and bacteria.
As countermeasures to the biofouling in the reverse osmosis membrane filtration plant, many techniques of adding a disinfectant which inhibits increase of the biofilm to treated water, and of adding a cleanser which cleans the reverse osmosis membrane were suggested. But, the method for accurately and easily evaluating or verifying effectiveness of condition for adding the disinfectant or cleanser by measuring degree of biofouling became a problem.
As the conventional methods for detecting biofouling, the first method is to analyze the structure of the biofilm itself without disassembling the reverse osmosis membrane or the biofilm, and uses atomic force microscope, optical coherence tomography, scanning electron microscope, magnetic resonance imaging, confocal laser scanning microscope and transmission electron microscope. But, there are problems that expensive devices and experts are needed, and only the biofouled surface can be checked.
The second method is a biological analysis method such as real-time monitoring of amplified product of PCR (real-time PCR), restriction fragment length polymorphism (RFLP) analysis, denaturing gradient gel electrophoresis (DGGE) gene analysis, fluorescence in situ hybridization and the like, but it has problems of taking several days and requiring experts.
The third method is to quantitatively analyze biofouling by biomass accumulation, and may include ATP measuring method, total direct cell count (TDC), heterotrophic plate count (HPC) and the like, but theses technologies has problems that it also needs expert knowledge, and consumes chemical enzyme. And TDC has a problem of large standard deviation, and HPC has a problem that only small part of the microorganism sample can be checked.
Therefore, a method which can quickly monitor degree of biofouling (biological contamination) without separation or disassembly of equipments such as a reverse osmosis membrane in a sea water desalination facility is needed, and further, there has been no biofouling monitoring method using a natural phosphor contained in brine in the sea water desalination facility.
Throughout this application, various publications and patents are referred and citations are provided in parentheses. The disclosures of these publications and patents in their entities are hereby incorporated by references into this application in order to fully describe this invention and the state of the art to which this invention pertains.